Monocrystalline thin foils were subjected to  in situ  heating, and the isothermal evolution of antiphase boundaries was investigated by means of transmission electron microscopy. It was recalled that antiphase boundaries played an important role in the phase changes of long-range ordered alloys. The grown-in domains were found to have a DO3 long-range ordered structure, with randomly shaped antiphase boundaries (swirl-shaped domains). At temperatures of up to 400C, there was no significant change in the domain or antiphase boundary structure. At a temperature of 500C, which was below the transition temperature (about 550C) from DO3 to B2, dislocation motion and coarsening of the domains was detected. The dislocations had a Burgers vector of a/4<111>. The dislocations dragged B2-type antiphase boundaries behind them. The reactions of the B2-type antiphase boundaries with DO3-type grown-in boundaries were analyzed. It was found that, with increasing annealing time, the density of B2-type boundaries increased and the size of the domains decreased. There was an associated thickening of the B2 domain walls.

A.Korner: Philosophical Magazine Letters, 1995, 72[1], 21-31